Breeders have been shortening finishing times for decades now, so that's incorrect.
Watts are uniquely dependent on the device they're fed into and more efficient led setups are appearing all the time.
@REALSTYLES built a 70% efficient COB LED light and was close to 2gpw. Others have mentioned they're knocking on the same door, again with COB LED. So that assertion is even further from the facts on the ground.
I absolutely think 2gpw is possible and with the new techniques and technologies I've seen recently, I'd say it's even likely to become an expected standard in the not too distant future.